1. Field of the Invention
This invention relates to adhesive compositions for hard human tissues such as tooth, bone, etc. More particularly, this invention relates to adhesive compositions such as adhesives for the treatment of a complex fracture of the bone, filling agents for the fixation of artificial joints, dental adhesives, dental filling materials, etc., which must retain powerful bond strengths under wet conditions.
2. Description of the Prior Art
As the prior art adhesive agents fo the fixation of artificial joints or dental filling agents, there are known mixtures of polymethyl methacrylate with methyl methacrylate, mixtures of bisphenol-A diglycidyl methacrylate with triethylene glycol dimethacrylate, etc. as cured with a radical-generating agent such as a peroxide-amine compound system. However, the cured mass obtained by the known method has little affinity for hard human tissues, the bond strength under wet conditions being as low as about 0 to 5 kg/cm.sup.2. For use as preventive filling agents or orthodontic cements, adhesives based on .alpha.-cyanoacrylates have been proposed recently to provide an improved adhesion with the dentinal tissue but these adhesives proved to have poor stability in the oral cavity and problems in connection with handling and application. The dental adhesives obtainable by the polymerization of methyl methacrylate with trialkylborons (Japanese Pat. Publications No. 14318/1967 and No. 29195/1970) have only a poor bonding affinity for the enamel, despite their favorable performance with respect to the dentin. It is also known that improved adhesion may be established by adding an addition-polymerizable organic phosphoryl monofluoride compound to a dental adhesive composition (U.S. Pat. No. 3,882,600) but the P-F bond in this compound brings forth safety problems because of the toxic nature of the fluorine compound.
It is further known that improved adhesion may be obtained by adding a divalent phosphoric acid containing a vinyl group allegedly capable of combining itself with the calcium in the tooth as an adhesive composition (Journal of Dental Research 53, 879-888, 1974). This product, however, is practically not sufficiently useful owing to its low bonding affinity.
It has recently been reported that certain monomers having the structure ##STR2## provide a durable and strong bond with the tooth enamel (Journal of Dental Research 56, 943-952, 1977) but the report does not refer to the question of adhesion to the dentin. Some of the present inventors previously discovered that phosphoric or phosphonic acid ester compounds having at least one radical-polymerizable functional group and a ##STR3## group have an excellent adhesive affinity for the tooth and particularly with respect to the dentin and accordingly filed patent applications U.S. Ser. No. 778,734 and No. 829,486). Nonetheless, we discovered that those phosphoric or phosphonic acid ester compounds leave something to be improved in respect of their stability under wet conditions.